High pressure methods and apparatus



July 4, 1967 A. ZEITLIN HIGH PRESSURE METHODS AND APPARATUS 2 Sheets-Sheet 1 Filed Dec. 30, 1963 42 INVENTOR.

c ALEXANDER ZEITLIN BY I (7 12, MW'FDMW his ATTORNEYS United States Patent 3 328 838 HIGH PRESSURE MIiTHbDS AND APPARATUS Alexander Zeitlin, White Plains, N.Y., assignor to Barogenics, Inc., New York, N.Y., a corporation of New York Filed Dec. 30, 1963, Ser. No. 334,429 9 Claims. (Cl. 18-16) This invention relates to apparatus for exerting high pressure by ram units on an object to be compressed. More particularly, this invention relates to apparatus of such sort wherein the ram units or portions thereof are immersed in a pressurized hydrostatic medium.

In high pressure apparatus with ram units, the units should be supported to each have an appropriate position and alignment relative to the object to be compressed. One such support means is the outer anvil cage which is disclosed in U.S. Patent 3,093,862, and which is comprised, in essence, of a hollow block containing the object and surrounded by the medium. The object is compressed by anvils driven towards the center of the block by the pressure of the medium on the back faces of inwardly movable rams having access to the inner space of the 'block by being seated in ports which pass through the block to such space. An annular seal means encircles each such ram to prevent the pressurized medium outside the block from flowing to its interior through the port in which the ram is received.

While such a cage has been more or less satisfactory, its exterior is subject to a heavy radially inward pressure loading from the pressure exerted by the pressurized medium. Therefore it has been necessary for the described cage to be of massive and strong construction.

It is an object of this invention to provide methods and apparatus whereby the support means for the ram units is not subject to a radially inward pressure loading by a pressurized medium which surrounds it.

Another object of this invention is to provide methods and apparatus whereby a ram unit is actuated by a pressurized medium in such manner that the pressure of the medium itself assists in sealing a portion or portions of the ram unit from being exposed to that pressure.

These and other objects are realized according to the invention by immersing the mentioned ram units and a fluid-pervious support means thereforin a pressurized medium and, further, by utilizing the pressure of such medium to actuate the units to compress a central object. Each of the units is so actuated by a forwardly-directed differential between forward and reverse pressure forces exerted by the medium on a piston which is movable within a wholly immersed cylinder to drive the ram of the unit. The forward pressure force is produced by having such cylinder open behind the piston in a manner whereby the medium comes into contact with and exerts pressure on the rear face of the piston. Such openness of the cylinder may be provided, for example, by having a perforate rear cylinder closure (or none at all) or by having apertures extending radially through the cylinder at the back end thereof. A cylinder which is so open is to be distinguished from one in which the cylinder provides behind the piston a chamber which is pressure tight and is closed except for one or more connections therewith of pressure-tight means for conveying a fluid medium to and/or from the chamber.

In order to provide the described forwardly-directed differential of pressure forces, the reverse pressure force, if any, must be less than the forward pressure force. Such lesser reverse pressure force is realized in the present invention by utilizing sealing means forward of the piston to shield a portion or portions of the ram unit from the pressure of the medium. The shielding is of such character that the cross section of the piston on which the 'ice medium can directly or indirectly exert reverse pressure is of lesser area than the pistons rear face on which the medium exerts forward pressure. Hence, the piston is subjected to a net forward force which drives it and the ram forwardly.

According to one aspect of the invention, the described differential of pressure forces on the piston is produced by having on its cylinder a front closure with an axial bore which is of smaller cross section than the piston, and through which there passes a ram stem encircled by annular seal means which obstructs passage of the medium reversely through the bore. Because the medium is so obstructed, its pressure is shielded or prevented from acting, in effect, reversely on the piston over a part of the cross section thereof. Therefore, the forward pressure force on the piston exceeds the reverse pressure force on it, and the piston and ram are driven forward.

According to another aspect of the invention, the described dilferential in pressure forces is produced by inserting the head of the ram in an entry port in means forming a closed envelope interposed between such head and the pressurized medium, and by providing annular seal means obstructing passage of the medium through such port. In this latter instance, the pressure of the medium is again prevented from acting, in effect, reversely on at least part of the cross-section of the piston. Thus, as before, the piston and ram are driven forward.

According to still another aspect of the invention, the two previously described ways of producing the forwardly directed differential are employed in conjunction with each other.

Because the support means for the ram units is pervious to the pressurized medium and is immersed therein, the fluid pressure acts upon the support means from all sides. In such circumstances, the support means is not subjected to a net radially inward pressure force from the medium. Moreover, as later described, the support means may be relieved of any reactive loading from the cylinders.

The fluid pressure forces act radially inward on the outside of each cylinder to tend to contract its inner diameter. Therefore, such forces tighten the seal between the inner Wall of the cylinder and the piston (and/or ram) contained in the cylinder.

While it is in accordance with the invention for the pressurized hydrostatic medium to be a gas or a solid adapted to have a more or less uniform hydrostatic pressure field developed therein, preferably such medium is a hydraulic fluid, such as Water, an organic hydraulic liquid or the like.

The character of the object to be compressed is not critical. Thus, for example, such object may be a mechanical part to be compacted or a charge material to be subjected to pressure. Also, it may be a pressure-receiving assembly comprised of such part or charge and of a casing therearound of a material (e.g., pyrophyllite, silver chloride) adapted under pressure to become plastic and to be transmissive of pressure in a substantially hydrostatic manner. In some applications of the invention, the object is compressed by direct contact therewith of each ram unit, and, in that instance the ram units usually (but not necessarily) taper at their front ends down to a relatively small front face which applies the pressure. According to one aspect of the invention, however, the object is not compressed by being directly contacted by ram units. Instead, the object is surrounded by a body of liquid, and the front ends of the ram units are utilized in a manner later described in detail to produce in that liquid a hydrostatic pressure which acts on the object to compress it.

The ram units are disposed around the object to exert balanced forces thereon. Apparatus according to the invention may be uni-axial in the sense that only two ram units are employed, the respective lines of action of those units being coincident with a single axis. Alternatively, such apparatus may be multiaxial in the sense that the respective lines of action of the ram units are coincident with more than one axis. For multiaxial apparatus to obtain a balance of forces on the object to be compressed, at least three ram units are required.

For a better understanding of the invention, reference is made to the following description of representative embodiments thereof and to the accompanying drawings wherein:

FIG. 1 is a plan view, partly in cross section, of apparatus embodying the invention, the cross section being taken as indicated by the arrows 11 in FIG. 2;

FIG. 2 is a front elevation in cross section of the apparatus of FIG. 1, the cross section being taken as indicated by the arrows 2-2 in FIG. 1, and parts of the apparatus to the rear of the cross-section plane being omitted from the figure in order to simplify the showing of FIG. 2;

FIG. 3 is an enlarged fragmentary view in cross section of a seal means utilized in the FIG. 1 apparatus;

FIG. 4 is a front elevation in cross section of the central portion of the FIG. 1 apparatus as modified to utilize an inner cage; and

FIG. 5 is a front elevation in cross section of a modification of the cage shown in FIG. 4.

In the description which follows, elements which are counterparts are designated by the same reference numeral but are distinguished from each other by different suffixes for their respective reference numerals. Unless the context otherwise requires, a description of any element is to be taken as equally applicable to all designated counterparts of that element.

Referring now to FIGURES 1 and 2, the reference numeral designates a pressure-containing shell which may be of spherical or other shape, but which is illustrated as being a tubular cylinder. The shell 10 is closed at its axially opposite ends by closure devices (not shown) so as to form a pressure-tight housing. Such housing may be similar to one of those disclosed in US. Patent 3,093,- 862 or similar to one of the pressure vessels disclosed in US. Patent 3,063,594.

The shell 10 is shown as containing a volume of a pressurized hydraulic fluid 11 such as water. Immersed in the fluid is a cubic multiaxial apparatus 12 and a cubic object 13 to be compressed. In the present instance, the object 13 is comprised of a central charge 14 and of a cubic pyrophyllite casing 15 around the charge. The six faces of casing 15 are individually contacted by six ram units 201140 mounted on six corresponding cross heads 21a- 21 which are parts of a hinged frame 16. Since each ram unit and its associated cross head has essentially the same structure as the others, only the ram unit a and its cross head 21a will be described in detail.

The ram unit 20a comprises a rearwardly flanged hydraulic cylinder 25a mounted on the crosshead 21a by bolts 23a passing through that crosshead and through the flange 26a of the cylinder. The cylinder 25a has an inner bore 24a and a piston 27a in the bore. The bore 24a is hydraulically open behind the piston in the sense that pressurized fluid 11 in container 10 can flow freely into the rear part of the bore through an aperture 28a in the crosshead. Because such aperture is of smaller diameter than the cylinder bore, the crosshead 21a is adapted to act as a rear stop for the piston.

The piston 27a is encircled at its front end by annular seal means 30a. While such seal means may be an ordinary O-n'ng seal, preferably it is a seal assembly similar to one disclosed in copending application Ser. No. l27,- 738, filed July 28, 1961, now Patent No. 3,156,475, issued Nov. 10, 1964, and owned by the assignee hereof.

Referring to FIGURE 3, the seal assembly 30a comprises an annular resiliently-expandable steel carrier ring 31a seated in an annular groove 32a in piston 27a, the ring 31a and the groove 32a being of rectangular crosssection. The steel ring 31a carries two seal rings 33a and 34a disposed as shown. Both of the rings 33a and 34a are made of rubber or other resiliently deformable material.

The FIG. 3 assembly operates as follows to seal the clearance 35a between the piston 27:: and the inner wall of the cylinder 25a. Pressurized fluid in the clearance leaks through the shown groove-seal interfaces 36a and 3711 as far as the seal ring 34a. Since the pressure of the fluid acts radially outward and radially inward on carrier ring 31a over separate areas which are relatively greater and lesser, respectively, the carrier ring is resiliently expanded by the fluid pressure to squeeze the seal ring 33a against the inner wall of the cylinder. Moreover, the pressure of the fluid acts forwardly on the carrier ring 31a to squeeze the seal ring 34a against the right side (FIG. 3) of the groove 32a. Hence, a negligible amount, if any, of fluid can leak in the axially forward direction past the described seal assembly 30a.

The ram unit 20a is also comprised of a ram a having a back portion or stand 41a disposed in the space 38a ahead of the piston within cylinder 250:. As shown, the

stand 41a makes rear face contact with the front face 39a of the piston. From a rear diameter approximating that of the piston, the stand 41a conically tapers in the forward direction down to a ram stem 42a connecting the stand to a ram head 43a outside the cylinder. The stem 42a passes with a sliding fit through an axial bore 44a in a front closure 29a for the cylinder, the bore 44a being of smaller cross-section than the piston 27a. Pressurized fluid 11 in the container 10 is obstructed from leaking in the reverse direction through bore 44a and into space 38a by an annular seal means 45a seated in the bore to encircle the ram stem. Such seal means may be of the type shown in FIG. 3.

At its front end, the ram head 43a has chamfered faces 47a which change the cross-sectional shape of the head from circular to square Those faces cause the head 43a to taper down to a square front face 46a by which the ram unit 20a applies pressure to a corresponding square outside face of object 13. The front face 46a of the ram unit 20a is somewhat smaller in size than the face contacted thereby of the object 13, and this is also true of the pressure-applying faces of the remaining ram units. Hence, the respective tapered head portions of the six ram units are separated by gaps 50 extending radially outward from the edges of the cubic object 13.

The crosshead 21a, is, as stated, a component of the frame 16,- the frame being hinged in accordance with the teachings of US. Patent 2,968,837. The manner in which the crosshead 21a is connected with the other frame components is as follows. The said crosshead has along its top margin a set of projections a (FIG. 2) separated by notches 56a, the projections having holes therethrough which register with each other to define a lengthwise passage through all the projections. The notches 56a form respective receptacles for the ends nearest crosshead 21a of a set of tie plates 57ab having holes therein which register with the holes in the projections 55a. A hinge pin 58a passes through the passage formed by the holes in the projections and in the tie plates so as to hingedly connect the crosshead 21a to the tie plates 57ab. At their ends remote from crosshead 21a, the tie plates 57ab are joined by a similar hinge connection to the crosshead 21b. Similar sets of tie plates 57ad, 57ae and 57a hingedly connect the crosshead 21a to, respectively, the crossheads 21d, 21e and 211. In like manner, every other crosshead is hingedly coupled to each crosshead adjacent thereto.

The bottom piston 27d differs from the others in that it has a rear plate 59d which rests against the crosshead 21d to hold up the piston 27d and ram 40d so that, when the object 13 is placed on the front face of the ram, that object is properly positioned for compression by the remaining rams. Moreover, the crosshead 21d differs from the others in that it has legs 60 to support frame 16 with in the container 10.

In operation, the container is initially empty of fluid. A cube 13 is placed on the front face of the ram 40d, and the circumferential rams 40a, 40c, 40c and 40 are advanced (by hand or appropriate tools) to bring the pressure-applying faces of those rams into engagement with the side faces of the cube. The crosshead 21b is then swung back into place and is fully reconnected. Next, fluid 11 is introduced into the container 10, and the fluid is pressurized.

Considering the ram unit 20a, the fluid exerts on pi-ston 27a a forward pressure force equal to the product of the fluid pressure p in space 11 and of the cross-sectional area r of the piston just to the rear of seal 33a (FIG. 3). That forward pressure force pr is opposed by a reverse force generated on the ram 40a by the fluid 11, such reverse force being transmitted through the ram to the piston. When the ram is out of contact with object 13, the reverse pressure force is equal to ps, the product of the fluid pressure p in space 11 and the cross-sectional area s of the stem 42a just forward of the seal 45 a. Because s is less than r, ps is less than pr, and, hence, the piston is subjected to a forwardly-directed force differential which drives the piston to cause the object 13 to be contacted by the front face 46a of the ram. Once that front face is in pressure contact with object 13, the fluid 11 exerts on ram 20a a reverse pressure force which (ignoring the effect of the later described gasket) is equal to p(sf) where is the area of the front face 46a. Since (s is evidently less than r, p(sf) is less than pr and the fluid pressure, accordingly, still urges the ram 20a forwardly by a force pr.p (sf). That forward force is, however, now opposed by a reverse force p where p is the reactive pressure exerted by the object 13 on the front face 46a.

In the discussion, hereinbefore and hereinafter, the inertial forces due to acceleration and deceleration of the ram unit are neglected because such inertial forces are negli gible in comparison to the pressure forces on the ram unit.

Apparatus of the sort described has a pressure-multiplying effect in that the pressure exerted by each of the ram units on the object being compressed is greater than the pressure applied to drive those units. In the press disclosed in US. Patent 2,968,837 wherein a pressurized fluid (in rearwardly closed cylinders) exerts forward force but no reverse force on each piston for each ram unit, the pres sure multiplying is effected in two stages by first providing for each unit a ram stem of lesser cross sectional area s than the cross sectional area r of the piston, and by then providing for the ram a pressure-applying front face of lesser area 1 than the stem cross sectional area s. In the instance of that press, the overall pressure multiplying factor is equal to the product of the ratios r/s and s/f or, in other words, r/f. Assuming that r is constant, the overall pressure multiplying factor can evidently be increased by decreasing f.

In the presently described apparatus, the overall pressure multiplying factor can be increased by decreasing s relative to r (the quantity r being assumed constant).

It might be thought, however, that, since the chamfered faces 47a of the ram unit 20a are subjected by pressurized fluid in the gaps 50 to a reverse pressure force which increases as those faces are axially lengthened to reduce the area f of the front face 46a, no appreciable pressure multiplying effect is afforded by the taper at the head of the ram, and there would be no advantage in reducing 1 relative to r and s (s being assumed less than r but greater than f). This is not so. By equating the axial forces which act on ram unit 20a, it can be shown that the pressuremultiplying factor m of such ram unit is given by the expression (r-s-i-f) /f. In this expression, as f is decreased, the numerator decreases less rapidly than the denominator, and the value of the expression accordingly increases-To put it another way, by calculating the partial derivatives 6m/6s and 6m/6f, it can be shown that a decrease in 1 produces an increase in m which is (rs) /ftimes greater than the increase in m produced by the same decrease in s. Therefore, in the present apparatus, the taper of the ram head does have a significant pressuremultiplying effect which increases as f is decreased. Moreover, the taper of the head is useful in that it permits the formation of the gasket now to be described.

Each of the ram units 2012-207 operates in the same way as unit 20a to compress the object 13. As pressure is applied to the object, some of the material of its casing 14 flows into the gaps 15 to there form a gasket which contains the pressure developed in the remainder of the casing material and transmitted from the rams through such material to the central charge 14. The pressure of the fluid 11 in gaps 50 aids in providing lateral support for the tapered side faces 47a of the rams, and such fluid pressure also aids in holding in the gasket so as to reduce the probability of a blow out thereof.

As the pressurized fluid 11 acts on ram unit 20a to drive its piston and ram forward, it also acts on the cylinder 25a to urge it rearwardly. This is so, because the effective cross-sectional area over which the fluid pressure acts reversely on the front closure 29a of cylinder 25a is greater by the value (r-s) than the effective cross-sectional area over which the fluid pressure acts forwardly on the cylinder. Therefore, the cylinder 25a reactively loads the frame 16 with a force equal to the product of the fluid pressure and the area (r-s). That reactive force is, however, less than the force pr (where p is fluid pressure) by which each of the ram units of the press of US. Patent 2,968,837 reactively loads its frame. Therefore, for a given 1 and a given r, the frame of the FIG. 1 apparatus can be made substantially lighter in construction than the frame required for the press of the last named patent.

Another advantage of the FIG. 1 apparatus is as follows: Assume that the apparatus has a pressure multiplying factor (rs+,f) /f of which the value In is the largest value for the factor which can safely be used with the material of which the ram heads are made. Now, providing that the quantity (r-s) is kept constant, each of the parameters r and s can be made as large as the structure will allow without changing the value of m and withoutincreasing the reactive load (rs) on the frame. In other words, the pistons, cylinders and the ram stems of the ram units can all be constructed to have a diameter approaching the side-to-side dimension of the frame itself. An increase in the diameter of the ram stem is advantageous because it minimizes the bending deflection of the stem as a column in response to the axial forces which are applied to the opposite ends of the stem.

The frame 16 is evidentially pervious to the fluid 11 and is surrounded on all sides by that fluid. Therefore, apart from the described reactive loading, the fluid exerts zero resultant fluid pressure force on the frame which, accordingly, need not be made strong for the purpose of withstanding contact by the pressurized fluid.

The sealing action in ram unit 20a of the assemblies 30a and 45a is aided by the radially inward force exerted around the exterior of cylinder 25a between those assemblies as a result of the differential between the full fluid pressure outside the cylinder and the absence of any such pressure in the space 38a within the cylinder. Such radially inward force tends to contract cylinder 25a to thereby tighten the seals of those assemblies to make them more effective. That effectiveness is further increased by the radial expansion of piston 27a and ram stem 43a in response to the axial compression of those elements by the oppositely directed axial forces on the piston-ram combination. The sealing action of the seal assemblies of the other ram units is aided in like manner.

Subsequent to a compression of an object 13, the ram units are retracted in a manner as follows: Considering the units 20a, the space 38a in cylinder 25a is connected by way of piping 70a to the outside of the pressure-tight housing of which shell 10 forms a part. During the driving of the ram units inward, the space 38a is vented through piping 70a to atmospheric pressure. After completion of a compressing operation, the pressure on the fluid 11 is released, the piping 70a is connected to a hydraulic pump (not shown) outside the housing, and other fluid under moderate pressure is then pumped from such pump through the piping 70a into the space 38a to drive the ram and piston rearwardly until the piston is stopped by the crosshead 21a. Thereafter, the pressure on the fluid in space 3842 is released by again venting piping 70a to the atmosphere. Retraction of the other ram units is effected in a similar manner.

FIGURE 4 shows the central portion of the FIG. 1 apparatus as modified to incorporate an inner cage 8-0. Such cage is shown as in the form of a hollow cubic block containing the object 13, although alternatively the cage 80 may be in the form, say, of the inner cage disclosed in US. Patent 3,093,862. Access to the object from the outside of the cage is provided by six cylindrical entry ports which extend through the cage to the interior thereof, port 810: being exemplary of the others. As shown, the stem 42a of ram unit 20a passes through the last named port. Annular seal means 82:: of the type disclosed in FIG. 3 is seated in the port 81a and encircles the ram stern 42a to obstruct passage of pressurized fluid through that port and into the cage interior which contains only air at atmospheric pressure; Since each of the other five ports is similarly sealed, the head 4%: of ram unit 23a and the object 13 are isolated from the pressurized fluid 11 in container by a closed envelope interposed between that fluid and those elements. The ram head is (FIG. 4) comprised of a cemented tungsten carbide anvil 83a and a pair of support rings 84:: and 85a shrink fitted onto the shank of the anvil.

Because the pressurized fluid 11 is isolated from the ram head 43a and, hence, cannot exert any reverse pressure forces on the tapered side faces of that head, the pressure multiplying factor of the ram unit is changed by use of the cage 80 to be equal to r/ the products of the ratios r/s and s/ f. In other words, the cage 80 permits the ram uni-t torealize the greatest pressure-multiplying factor which can characterize the configuration of that unit. At the same time, the reactive loading from ram unit 20a on the frame 16 remains at its previous value of p(rs). The cage 80 is, of course, subjected to the full pressure p of the fluid 11 because (apart from some slight pressurizing of the air inside cage 80' by the advancement of the ram heads) there is no pressure inside the cage to counterbalance the fluid pressure on the outside thereof. The full pressure loading of the fluid on the cage is, however, offset by the fact that cage 80 is an inner cage of relatively small exterior area. Therefore, the cage 80 can, without difliculty be constructed to withstand the fluid pressure thereon.

When using the cage 80, the ram stem 42a can be made of the same diameter as the piston 27a (FIG. 1), the size of the port 8111 in the cage 80 being correspondingly increased. When the piston and ram stern are of equal diameter, the reverse fluid pressure force on the cylinder a is reduced to equal the forward pressure force on the cylinder, wherefore cylinder 25a exerts no reactive load on the frame 16, and both the frame and the cylinder may be considered as floating in the pressurized fluid. A pressure-multiplying factor r/f is still obtained because there is still no reverse pressure force on the piston 27a. The elimination in such manner of the reactive loading on frame 16 permits the frame to be of very light construction because its only function is then to position and align the cylinders of the ram units so as to guide the pistons and rams thereof to follow appropriate lines of action for compressing the object 13. In such instances, the seals of the ram units perform no useful function and may be removed.

The same effect (with the FIG. 4 modification) of elimination of all reactive loading on frame 16 may, of

course, be obtained by keeping the ram stems of lesser diameter than that of the pistons, and by allowing fluid to enter the cylinders ahead of the pistons by removing the forward seals of the cylinders or by other means. When such is done, however, the pressure multiplying factor drops from r/f to s/f.

FIGURE 5 shows a modification of the FIG. 4 cage in which the object 13 within cage has been replaced by a body (such as a mechanical part) designated as and by a volume of a hydraulic liquid 91 in which the piece 90 is immersed. The driving of the ram head into the cage 80 serves to develop in the liquid 91 a high hydrostatic pressure which compacts the piece 90. In the FIG. 5 modification, a tapered configuration for the ram heads would perform no useful function. Therefore, those heads may be blunt as represented by the head 43a for the ram unit 20a. As a further change, because the pressure of the liquid 91 builds up from a value less than to a value greater than that of the pressure of the actuating fluid 11 which surrounds the cage 80, the seals for the entry ports of the cage should seal in both directions. Inasmuch as the blunt faces of the ram heads each have an area the same as the cross-sectional area s of each ram stern, a pressure multiplying factor of r/s is obtained for the FIG. 1 apparatus as modified in accordance With FIG. 5.

Some exemplary dimensions for the described apparatus are 30" for the inner diameter of container, 16" for the diameter of the pistons, 6" for the diameter of the ram stems, and 1.45" on a side for the square front faces of the rams.

The above described embodiments being exemplary only, it is to be understood that additions thereto, modifications thereof and omissions therefrom can be made without departing from the spirit of the invention, and that the invention comprehends embodiments differing in form and/or detail from those which have been specifically described.

Thus, for example, the front ends of the cylinders of the FIG. 1 apparatus may be connected to each other by crossheads and hinged linkages (like those shown as connecting the rear ends of the cylinders) so as to increase the stability of the frame. If desired, the space occupied by the frame 16 may be reduced by hingedly connecting the frames various sets of tie plates directly to the rear flanges of the hydraulic cylinders instead of to crossheads bolted to those flanges. The apparatus need not be of cubic configuration but may be tetrahedral, octahedral, etc. Instead of cage 80 being in the form of a cube or other polyhedron, it may be, say, in the form of a hollow sphere appropriately apertured by entry ports. Neither object 13 (FIGS. 1 and 4) nor object 90 (FIG. 5) need be of the form shown but, instead, each may be, for example, a powdered charge encapsulated in a thin envelope of some fluid impervious material (i.e., rubber, plastic, metal foil). Moreover, the object 13 may be a workpiece which is formed into a desired shape by dies on the front ends of the ram units. In the instance where an inner cage is of used (FIGS. 4 and 5), the stems and heads of the ram units may be separate, the heads being in the form of short forwardly tapered cylinders contained in the inner cage bores and having rear faces with which front faces on the stems make contact to urge the heads forwardly. The advantage in so making the ram heads discontinuous with the ram stems is that the heads are freely alignable with the bores in which they are received rather than having a fixed alignment determined by that of the ram stems.

Further, it is to be understood that, unless the context otherwise requires, all of the variants which have been described in connection with FIG. 1 are applicable also to the FIG. 1 apparatus as modified in accordance with FIG. 4 and/ or FIG. 5.

Accordingly, the invention is not to be considered as limited save as is consonant with the recitals of the following claims.

I claim:

1. Apparatus comprising, a ram unit comprised of a hydraulic cylinder which has a movable piston therein and which is hydraulically open behind said piston, and a ram forward of and drivable forwardly by said piston and having a back end in said cylinder and a head forward thereof, said apparatus further comprising a container both for said unit and for a volume of pressurized hydraulic fluid in which said cylinder is immersed to have the rear face of said piston contacted by said fluid and urged forwardly thereby, and sealing means interposed between said fluid and at least one portion of said ram unit forward of the rear face of said piston, said sealing means being an obstruction to the reversely directed exertion on such portion of the pressure of said fluid, said apparatus further comprising positioning means for holding an object to be compressed within said container and support means for mounting said ram unit so that its line of action coincides with an object held by said positioning means.

2. Apparatus as in claim 1 in which said cylinder has a front closure with an axial bore therethrough of smaller cross-section than said piston, said ram has between said back end and head a stern slidably received within said bore, and in which said sealing means comprises annular seal means disposed around said head, said seal means being an obstruction to flow of said fluid reversely through said bore to the inside of said cylinder.

3. Apparatus as in claim 2 in which said sealing means further comprises envelope means immersed in said fluid and having an entry port in which said ram head is slidably received to project into the interior of such means, and annular seal means disposed around said head, said last-named seal means being an obstruction to passage of said fluid through said port to said interior.

4. Apparatus as in claim 1 in which said sealing means comprises envelope means immersed in said fluid and having an entry port in which said ram head is slidably received to project into the interior of such means and annular seal means disposed around said head, said lastnamed seal means being an obstruction to passage of said fluid through said port to said interior.

5. Apparatus comprising, a plurality of ram units each comprised of a hydraulic cylinder which has a movable piston therein and which is hydraulically open behind said piston, and a ram forward of and drivable forwardly by said piston and having a back end in said cylinder and a head forward thereof, said apparatus further comprising, support means pervious to hydraulic fluid and by which said ram units are mounted in an alignment for which their respective lines of action are directed towards a common central compressing zone within said support means, a container both for said support means and units and for a volume of pressurized fluid in which the cylinder of each of said units is immersed to have the rear face of the piston in such cylinder contacted by said fluid and urged forwardly thereby, and sealing means interposed between said fluid and at least one portion of each ram unit forward of the rear face of its piston, said sealing means being an obstruction to the reversely di- 10 rected exertion on such portion of the pressure of said fluid.

6. Apparatus as in claim 5 in which said plurality of ram units includes at least three such units, and in which said lines of action are multiaxial.

7. Apparatus as in claim 5 in which said support means is a closed hinged frame comprised of a plurality of support crossheads respective to said units and of a plurality of hinged couplings by which adjacent ones of said crossheads are coupled to each other.

8. In pressure multiplying apparatus having a plurality of ram units comprised of hydraulic cylinders and pistons and of rams driven forward by said pistons, and having, also, a frame which is pervious to hydraulic fluid and by which said ram units are mounted to have their respective lines of action directed towards a common central compressing zone within said frame, the improvement in which each ram unit is open behind the piston thereof to a pressurized fluid medium surrounding the cylinder thereof, said improvement further comprising, a container for both said frame and units and for a pressurized medium in which said frame and units are immersed to have the rear face of the piston of each unit contacted by said medium and urged forwardly by the pressure thereof, and sealing means disposed around each ram unit forward of the rear face of the piston thereof to create a forwardly directed differential between the forward and reverse fluid pressure forces exerted on such piston by said medium.

9. Apparatus comprising, a multiaxial array of ram units each comprised of a hydraulic cylinder which has a piston therein and is hydraulically open behind said piston, and which has a front closure with an axial bore therethrough of smaller cross-section than said piston, a ram forward of and drivable forwardly by said piston and having a back end in said cylinder and a head forward therof, said back end and head being coupled by a ram stem slidably received within said bore, and said head being tipped by an anvil portion tapering in the forward direction down to a pressure-applying front face for said ram, annular seal means disposed around said stem, said seal means being an obstruction to flow of hydraulic fluid reversely through said bore to the inside of said cylinder, a frame pervious to hydraulic fluid and by which said drive units are mounted in said array to have the respective lines of actions thereof converge multiaxially on a common central compressing zone within said frame, said apparatus further comprising a container both for said frame and ram units and for a volume of pressurized hydraulic fluid in which said frame and ram units are immersed to have the rear face of the piston of each unit contacted by said fluid.

References Cited UNITED STATES PATENTS 2,968,837 1/1961 Zeitlin et al. 3,093,862 6/1963 Gerard et al.

WILLIAM J. STEPHENSON, Primary Examiner. 

1. APPARATUS COMPRISING, A RAM UNIT COMPRISED OF A HYDRAULIC CYLINDER WHICH HAS A MOVABLE PISTON THEREIN AND WHICH HYDRAULICALLY OPEN BEHIND SAID PISTON, AND A RAM FORWARD OF AND DRIVABLE FORWARDLY BY SAID PISTON AND HAVING A BACK END IN SAID CYLINDER AND A HEAD FORWARD THEREOF, SAID APPARATUS FURTHER COMPRISING A CONTAINER BOTH FOR SAID UNIT AND FOR A VOLUME OF PRESSURIZED HYDRAULIC FLUID IN WHICH SAID CYLINDER IS IMMERSED TO HAVE THE REAR FACE OF SAID PISTION CONTACTED BY SAID FLUID AND URGED FORWARDLY THEREBY, AND SEALING MEANS INTERPOSED BETWEEN SAID FLUID AND AT LEAST ONE PORTION OF SAID RAM UNIT FORWARD OF THE REAR FACE OF SAID PISTON, SAID SEALING MEANS BEING AN OBSTRUCTION TO THE REVERSELY DIRECTED EXERTION ON SUCH PORTION OF THE PRESSURE OF SAID FLUID, SAID APPARATUS FURTHER COMPRISING POSITIONING MEANS FOR HOLDING AN OBJECT TO BE COMPRESSED WITHIN SAID CONTAINER AND SUPPORT MEANS FOR MOUNTING SAID RAM UNIT SO THAT ITS LINE OF ACTION COINCIDES WITH AN OBJECT HELD BY SAID POSITIONING MEANS. 